Java Oops Quiz

Inheritance in Java allows a new class (subclass) to inherit properties and behaviors (fields and methods) from an existing class (superclass). This promotes code reusability by avoiding code duplication. Subclasses can also add their own unique features or modify inherited behaviors, making the code more adaptable and organized.

The private access modifier is the most restrictive access level in Java. It limits access to a class member (field or method) to within the same class only. This enforces encapsulation by preventing external code from directly accessing or modifying the internal data of an object.

An interface in Java is a contract that defines a set of methods that implementing classes must provide. It specifies the behaviors that classes should exhibit but doesn't provide the implementation details. Interfaces promote abstraction and flexibility in code design.

Encapsulation is the practice of bundling data (fields) and the methods that operate on that data within a class. It restricts direct access to the data from outside the class, forcing interaction through defined methods. This protects data integrity and promotes modularity.

Method overriding involves providing a specific implementation for a method that is already defined in a superclass. This allows subclasses to customize inherited behaviors. Method overloading, on the other hand, involves defining multiple methods with the same name but different parameters in the same class.

A constructor is a special method with the same name as the class. It is automatically called when a new object of that class is created. Its primary role is to initialize the object's fields, ensuring that the object starts in a valid and usable state.

The this keyword in Java refers to the current object within a non-static method or constructor. It's used to differentiate between instance variables and local variables or method parameters when they have the same name. It can also be used to call other constructors within the same class.

An abstract class can have both abstract and non-abstract methods. Abstract methods are declared without an implementation, acting as placeholders for subclasses to provide concrete implementations. Non-abstract methods have complete implementations and can be used directly by the abstract class or its subclasses.

Polymorphism, meaning "many forms," allows objects of different classes to be treated as objects of a common type. This is achieved through method overriding, where a subclass provides a specific implementation for a method already defined in its superclass. At runtime, the appropriate method is called based on the actual object's class.

An abstract class can have constructors, while an interface cannot. Constructors are used to initialize the state of an object when it's created. Since interfaces cannot be instantiated directly, they don't have constructors. Abstract classes, however, can be used as base classes for inheritance.